The Jiangmen Underground Neutrino Observatory (JUNO) is a low background 20 kton liquid scintillator multi-purpose experiment located in Kaiping, Jiangmen, China. Its physics goals include the determination of the neutrino mass ordering as well as the oscillation parameters using reactor neutrinos. JUNO will be instrumented with approximately 20,000 20-inch photomultiplier tubes (PMTs) of two types (dynode and micro-channel plate). These PMTs are tested for their general performance in a PMT testing facility located in Zhongshan, China. A major component of the testing system are the four commercial shipping containers, which are modified and equipped with commercial DAQ (three containers) and final JUNO electronics (one container, currently in installation), featuring 136 channels in total. Two containers (72 channels) are used for the characterization of each PMT. This poster presents the capabilities and performance parameters of the containers as well as exemplary results from the PMT testing.